Modeling and minimization for thermal stress birefringence of an optical voltage transducer

The thermal stress birefringence (TSB) is a big issue that destroys the sensing stability of the optical voltage transducer (OVT), and the existing research on the theoretical modeling and solution are not good enough to handle it. This paper presents a mathematical model of the TSB based on the photo-elastic effect, and then it is quantitatively calculated through the multiphysics coupling simulation. It shows that the asymmetric radial stresses in the electro-optic crystal are the root cause for the TSB, which results in a phase delay greater than 3.153°. On this basis, a method for TSB minimization to use the polyurethane buffer layer to enwrap around the crystal is proposed, which eliminates the random radial stress and improves the symmetry of stress distribution. Finally, the effectiveness of the proposed method is verified by simulation and experiment.